The present invention relates generally to an ignition timing device. More particularly, the present invention relates to an ignition timing device for use on Harley-Davidson(trademark) engines.
As is well known, the ignition spark used for detonation in an internal combustion engine must be timed to the position of a piston reciprocating within the combustion chamber. In order to time the engine, the manufacturer generally provides a timing mark that rotates while the engine is running. A timing light monitors the ignition system and provides a strobed light that corresponds with the firing of a particular spark plug. When illuminated by the timing light, the mark appears substantially stationary with respect to a fixed reference. The mechanic adjusts the ignition system to position the timing mark at a desired location with respect to the fixed reference. This procedure thereby adjusts the timing of the ignition spark relative to the position of the reciprocating piston.
Some internal combustion engines are particularly troublesome to time. A Harley-Davidson(trademark) engine is known for its difficulty. To time the Harley-Davidson(trademark) engine, the mechanic removes a timing plug of a timing port in the crankcase to expose a flywheel. The timing mark is located on the flywheel and can be seen through the timing port. The mechanic points a timing light into the timing port and notes the position of the timing mark as strobed by the timing light. Unfortunately, removal of the timing plug and operation of the engine causes an oil mist to emerge from the timing port. The emerging oil makes the timing mark difficult to see as well as typically covers the mechanic and the surrounding area with oil.
One prior art technique for controlling the oil mist includes inserting a clear plastic plug into the timing port. The clear plastic plug is supposed to block the oil mist and allow visibility of the timing mark. However, the inside surface of the plug is substantially covered with oil, which obscures visibility of the timing mark.
Other devices have been proposed for timing the Harley-Davidson(trademark) engine. For instance, U.S. Pat. No. 5,814,723 issued to Berardinelli uses a light transmissive channel that couples light from the timing light into the timing port, while a second light transmissive channel carries light reflected from the timing mark out of the engine case. Although this device may allow easier visibility of the timing mark, one shortcoming includes the fact that the timing port is located on one side of the engine and the ignition adjustment is located on the other. Therefore, a mechanic operating by himself would find viewing the timing mark and adjusting the engine still to be difficult.
Other U.S. Patents disclose yet further devices for timing the Harley-Davidson(trademark) engine. U.S. Pat. No. 5,431,134 discloses a Harley-Davidson(trademark) engine ignition timing device which electronically determines top dead center (TDC) positioning and the degrees of spark ignition before or after TDC to permit dynamic setting and monitoring of the engine ignition timing. The timing device uses a conventional inductive clamp to sense a spark and an optical sensor for sensing the position of the engine. This patent further teaches the installation of additional components onto the motorcycle such that the optical sensor may provide a signal based upon camshaft position via the installed components. However, in order to accommodate the wide array of ignitions systems used on Harley-Davidson(trademark) motorcycles, this patent employs various different hardware additions to be installed on the various different systems. Some portions of the hardware additions permanently remain on the motorcycle engine.
Thus, there is a continuing need for a simple, reliable ignition timing device for use on Harley-Davidson(trademark) engines or other engines having a timing port in a crankcase. The improved ignition timing device should address one, some or all of the shortcomings discussed above.
An ignition timing device is provided for timing an engine having a timing port and a timing mark indicative of a position of a movable member. The ignition timing devices includes a sensor adapted to be secured in the timing port to provide a timing mark signal indicative of presence of the timing mark. Further, an ignition sensor is adapted to provide an ignition signal indicative of the occurrence of an ignition spark. A filter receives the ignition signal and provides a filtered ignition signal. The filter filters ignition sparks of compression strokes from ignition sparks of compression and exhaust strokes of a selected cylinder to provide the filtered ignition signal. A delay element receives the filtered ignition signal and provides a delay signal having a selected delay from the filtered ignition signal. Also, a comparator receives a timing mark signal and the delay signal in order to provide an output signal indicative of substantial simultaneous occurrence of the timing mark signal and the delay signal. Additionally, an indicator receives the output signal and is operable as a function thereof.
Another aspect of the present invention is a method for timing an engine having a timing port through which a timing mark indicative of a position of a movable member of the engine can be seen. The method includes securing a variable reluctance sensor proximate the timing port. Furthermore, the presence of the timing mark of the engine is sensed with the variable reluctance sensor and provides a timing mark signal as a function thereof. Also, the method includes sensing an occurrence of an ignition spark and providing an ignition signal as a function thereof. Furthermore, ignition sparks of compression strokes and ignition sparks of compression and exhaust strokes of a selected cylinder are filtered and a filtered ignition signal is provided being indicative of only the ignition sparks of compression strokes. The method further includes generating a delayed signal having a selected delay from the filtered ignition signal. Also, the delay signal and the ignition signal are compared and an output signal indicative of substantial simultaneous occurrence of the timing mark signal and the delayed signal is provided. Also, an indicator is operated as a function of the output signal.
In another aspect, a variable reluctance sensor is provided for use within an ignition timing device. The variable reluctance sensor includes a support tube insertable in a bore extending from a first end to a second end. Furthermore, a sensor housing is insertable in the bore. Also, a variable reluctance probe is disposed in the sensor housing.